Alloy steels and articles thereof



United States Patent Ofiiice 3,219,442 Patented Nov. 23, 1965 3,219,442 ALLOY STEELS AND ARTICLES THEREOF Harry G. Johnstin, Latrobe, Pa., assignor to Vasco Metals Corporation, a corporation of Pennsylvania No Drawing. Filed Oct. 30, 1964, Ser. No. 407,845 9 Claims. (Cl. 75128) This application is a continuation-in-part of my copending application Serial No. 99,712 filed March 31, 1961, now abandoned.

This invention relates to alloy steels and especially to alloy steels having good hardness retention and wear resistance at high temperatures. One aspect of the invention is concerned with alloy steel suitable for use in the manufacture of hot forging dies. Another aspect is the provision of vanadium-containing steels having improved grindability.

Hot forging dies are employed in the forging of blades or vanes for jet engines from various types of high temperature-resistant and corrosion-resistant materials, such as stainless steel, titanium, and other metals or alloys exhibiting favorable properties at temperatures in jet engines. Alloy steels in the class of die steels vary in composition over a wide range. The steels for hot forging dies often cannot be cooled suificiently to prevent the dies from becoming very hot. In such dies, the steel must have a good hardness retention, which is not reduced by heating of the die to or near the maximum temperature used in tempering. The steel of hot forging dies must also resist distortion under mechnaical stresses in the forging operation. High mechanical stresses on the dies are encountered in the forging of some metals or alloys. A steel which is resistant to distortion or sinking of the die preferably should have a hardness of at least about 50 Rockwell C at room temperature.

Along with the foregoing factors, the steel used as a hot forging die should be wear-resistant, machinable, tough, grindable, and substantially corrosion-resistant when in contact with the metal being shaped or forged in the forging operation.

It is an object of this invention to provide new and improved alloy steels.

Another object of the invention is to provide alloy steels having high hardness.

A further object is to provide an alloy steel with high hardness and good wear resistance having acceptable grindability.

Still another object of the invention is to provide alloy steels suitable for use in the manufacture of forging dies.

A further object is to provide a process of manufacture for said improved alloy steels.

Another object is to provide hot forging dies and other articles of manufacture made of said improved alloy steels.

These and other objects of the invention are achieved by using alloy steels having the compositions:

The remainder of the alloy steels is substantially all iron, together with any alloying impurities which may be present in alloy steels.

The alloy steels of this invention are capable of attaining high hardness when properly austenitized, quenched and tempered.

A narrower range, which is preferred for alloy steels especially adapted for use as alloy steels in the manufacture of forging dies, is as follows:

Approximate percent by weight Carbon 0.80-1.00 Silicon 0.70-1.10 Manganese 0.20-0.40 Chromium 6.00-8.50 Vanadium 2.10-2.60 Molybdenum 1.00-2.00 Nickel -1 0-0.30 Phosphorus 0-0.20 Sulfur 0-0.20

Specific examples of alloy steels contemplated by the invention are tabulated below, wherein the unaccounted percentage consists substantially of iron.

Specific examples Example C Si Mn Cr V Mo P S Ni The heat treatment of the alloys of this invention preferably involves the steps of heating the alloy compositions to an austenitizing temperature in the range of about 1800 to 2100 F. The austenitized alloys may be either cooled in still air to room temperature or thereabouts or may be quenched in warm oil or in salt. The alloys are thereafter tempered at 900-1100 F., using either a single tempering stage or multiple tempering stages, such as triple tempering.

The advantages of the alloys of this invention will be further understood from the following examples in which the hardness and other physical characteristics of the alloys were determined under various conditions of heat treatment.

Example 5 The alloy of Example 1 was cast as a 1,000 1b., 10" ingot and forged to a 6" square billet. Samples 6" square and 1 /2" thick were taken from the top of the billet in the determination of hardness of the heat treated samples. To assure accurate hardness readings, cross-sectional faces were ground parallel.

The heat treating procedure involved the preheating of the samples in salt baths to a temperature of 1600 F. One sample was heated to 1800 F., another to 1850 F., another to 1900 F., another to 1950 F., another to 2000" F. and still another to 205-0 F. They were held at the respective temperature for 45 minutes and then cooled in still air to room temperature.

Thereafter, each sample was tempered for six hours at 900 F. and then for 6 hours at 950 F., then for 6 hours at 1,000 F., then at 1,-050 F. and finally at 1100 F. The hardness of the samples in the as-quenched state and after the cumulative tempers is reported in Table I.

Cumulative tempers.

Examination of micro specimens after tempering at 900 F. showed no marked variation in grain size in th range of quenching temperatures. The grain size was relatively good in all samples.

Example 6 Test blocks, 6" x 6" x 6" of the alloy steel of Example 2 were heat treated by pack hardening in spent pitch coke. A /2" diameter hole was drilled approximately 1" in from one corner in each block with a depth of about 5" for the insertion of an indicating rod. One block each was austenitized at 1860 and 1925 F. for a period of 1 /2 hours at temperature. In each instance, preheating was done at 1600 F. It required four hours to bring the first block from 1600 F. to 1860 F. The time required for the piece austenitized at 1925 F. was approximately the same. After giving the samples the required amount of time at the austenitizing temperature, the pieces were withdrawn for normal cooling in still air to room temperature. The samples were subjected to cumulative temperings at 950, 1000, 1050 and 1100 F. for 5 hours at temperature. Both the bearing and testing surfaces were ground prior to taking Brinell hardness readings.

TABLE II.-B RINELL HARDNESS Austenitized at 1,860F.

Tempering temperature 1 from Center block corners and edges Rockwell C 59-61 (by conversion) Rockwe l "0 59 Rockwe l O 56 Rockwell C 41 TABLE III.-B RINELL HARDNESS Austenitized at 1,925F.

Tempering temperature 1 from Center block corners and edges Rockwell C 61-63 (by conversion) Rockwel C 59 Rockwe 1 O 56 Rockwell C 44 4 The annealed hardness of the blocks was Brinell 228241.

Example 7 Test samples 6" square x 1 /2" thick were taken from the alloy of Example 3 and treated from austenitizing temperatures of 1860 and 1925 F. The blocks were preheated in salt at 1600 F. before transferring to the higher temperatures. After each block reached the austenitizing temperature, it was held for 1 /2 hours before being withdrawn for normal cooling in still air.

Grain count from 1925 F. showed 10.2 by the Intercept Method. The grains were not suificiently developed at 1860 F. to get a grain count.

Both blocks were subjected to cumulative temperings at 1000, 1050 and 1060 F. for three hours. The hardness at various stages of the tempering treatment is reported in Table IV.

TABLE IV Hardness Rockwell O Austenitizing temperature 1st 2d temper 1st 2d temper Retemper temper 1,000 F. temper 1,050 F. 1,060 F. 1,000 F. 1,050 F.

Example 8 Mn S P Cr Mo V 0.009 7. 40 1. 56 2. 60 0. 014 7. 58 l. 60 2. 48 0. 009 7. 39 1. 54 1.98 0.014 5. 31 1. 13 4. 08 0. 008 7. 53 1. 50 None the remainder in each case being iron.

Samples of the heats were austenitized, quenched and tempered at various austenitizing temperatures in the range of 1800 F. to 2100 F., cooled in still air, and tempered at temperatures in the range of 900 F. to 1100 F. to obtain specimens of each heat at various hardness levels.

An unusual grindability characteristic was noted when grindability tests were made. The steel containing 4.08% vanadium had poor grinding properties. At a hardness R0 of 58.7 the grinding ratio was 0.8 (cubic inches of metal removed/cubic inches of wheel wear). In other words, the wheel wear was greater than the amount of metal removed. At approximately the same hardness (58.6 Rc), the grinding ratio of Heat Number 75285 was 3.3. At approximately the same hardness, heat C324 had a grinding ratio of about 6. Heat C323 had a grinding ratio slightly less than that of heat 75285 at the same hardness.

In comparing these various alloy steels, therefore, it is noted that the grindability is at a maximum between approximately 2% and 2.6% vanadium. Beyond that from the standpoint of grindability there is no advantage over 0% vanadium. However, the grindability is still acceptab e p o approximately 2.84% vanadium. It has here- Heat C211 Heat A6379 Hardness, Impact Hardness, Impact Re strength, Rc strength,

i ft -lbs. it.-lbs.

Each impact strength result reported above represents the average result obtained on ten specimens of the respective Heats at each stated hardness level. The results, therefore, represent accurately the impact strength characteristics. The alloy of the present invention (Heat A6379) had markedly better impact strength characteristics at each comparable hardness level.

Thus, the alloy steels of this invention are especially adapted to be used where high hardness, good Wear resistance, good grindability and good hardness retention at high temperatures is a requisite for the steel. These alloy steels are especially adapted to be used as the steels in hot forging dies and other articles where the characteristics of the alloy steels herein described lend themselves to providing a good product.

The invention is hereby claimed as follows:

1. An alloy steel consisting essentially of the following in percent by weight: carbon, 0.801.30%; silicon, 0.1- 2.00%; manganese, 0.102.00%; chromium, 6.00- 10.00%; vanadium, 2.002.84%; molybdenum, 1.00 3.90%; nickel, 00.50%; phosphorus, 00.70%; and sulfur, 00.70% with the remainder being substantially all iron.

2. An alloy steel consisting essentially of the following in percent by weight: carbon, 0.801.00%; silicon, 0.70- 1.10%; manganese, 0.200.40%; chromium, 6.008.50%; vanadium, 2.10-2.60%; molybdenum, LOO-2.00%; nickel, 00.30%; phosphorus, 00.20%; and sulfur, 0-0.20% with the remainder being substantially all iron.

3. An alloy die steel which is wear resistant, machin able, tough and has good grindability which consists essentially of the following components in the approximate stated percents by Weight: carbon, 0.83%; silicon, 0.92%; manganese, 0.29%; chromium, 7.58%; vanadium, 2.48%; molybdenum, 1.60%; phosphorus, 0.014%; sulfur,

6 0.021%; and nickel, 0.16% with the remainder being substantially all iron.

4. An alloy die steel which is wear resistant, machinable, tough and has good grindability which consists essentially of the following components in the approximate stated percents by weight: carbon, 0.84%; silicon, 0.90%; manganese, 0.29%; chromium, 7.75%; vanadium, 2.60%; molybdenum, 1.60%; phosphorus, 0.010%; sulfur, 0.026%; and nickel, 0.010% with the remainder being substantially all iron.

5. An alloy die steel which is Wear resistant, machinable, tough and has acceptable grindability which consists essentially of the following components in the approximate stated percents by Weight: carbon, 0.85%; silicon, 0.92%; manganese, 0.26%; chromium, 7.58%; vanadium, 1.98%; molybdenum, 1.50%; phosphorus, 0.008% and sulfur, 0.021%; with the remainder being substantially all iron.

6. An alloy die steel which is Wear resistant, machinable, tough and has acceptable grindability which consists essentially of the following components in the approximate stated percents by Weight: carbon, 0.92%; silicon, 0.98%; manganese, 0.28%; chromium, 7.81%; vanadium, 2.84%; molybdenum, 1.41%; phosphorus, 0.012% and sulfur, 0.021%; with the remainder being substantially all iron.

7. A hot forging die made of an alloy steel consisting essentially of the following in percent by Weight: carbon, 0.801.30%; silicon, 0.12.00%; manganese, 0.10- 2.00%; chromium, 6.0010.00%; vanadium, ZOO-2.84%; molybdenum, LOO-3.90%; nickel, 00.50%; phosphorus, 00.70%; and sulfur, 00.70% with the remainder being substantially all iron.

8. A hot forging die made of an alloy steel consisting essentially of the following in percent by weight: carbon, 0.801.00%; silicon, 0.70l.10%; manganese, 0.20- 0.40%; chromium, 6.008.50%; vanadium, 2.10-2.60%; molybdenum, 1.002.00%; nickel, 0-0.30%; phosphorus, 00.20%; and sulfur, 00.20%; With the remainder being substantially all iron.

9. A process for manufacture of an alloy steel of high hardness and good hardness retention which comprises forming an alloy steel consisting essentially of carbon, 0.804210%; silicon, 0.12.00%; manganese, 0.10 2.00%; chromium, 6.0010.00%; vanadium, ZOO-2.84%; molybdenum, 1.003.90%; nickel, 00.50%; phosphorus, 00.70%; and sulfur, 00.70% with the remainder being substantially all iron, austenitizing said alloy steel at about 1800-2100 F., quenching said austenitized alloy steel, and tempering the quenched alloy steel at 900- 1100 F.

References Cited by the Examiner UNITED STATES PATENTS 1,778,226 10/1930 Nelson 148-143 XR 2,572,191 10/1951 Payson 148l34 XR 2,949,356 8/1960 Hughes l28.85

FOREIGN PATENTS 445,651 4/ 1936 Great Britain.

DAVID L. RECK, Primary Examiner. 

1. AN ALLOY STEEL CONSISTING ESSENTIALLY OF THE FOLLOWING IN PERCENT BY WEIGHT: CARBON, 0.80-1.30%; SILICON, 0.12.00%; MAGANESE, 0.10-2.00%; CHROMIUM, 6.0010.00%; VANADIUM, 2.00-2.84%; MOLYBDENUM, 1.003.90%; NICKEL, 0-0.50%; PHOSPHORUS, 0-0.70%; AND SULFUR, 0-0.70% WHITH THE REMAINDER BEING SUBSTANTIALLY ALL IRON. 